/Engine/Source/Runtime/Core/Public/Misc/MapErrors.h
{Volume} causes damage, but has no damagetype defined.: This warning is caused when there is a volume that is set to cause damage but doesn't have a damage type defined. A damage type is important because it tells the game code how to handle a actor's reaction to taking damage. This can be solved by going to the actor's Property Window->Physics Volume and setting the 'DamageType' property.
static [FLazyName](API\Runtime\Core\UObject\FLazyName) NoDamageType;